This study has been cancelled before initiation due to company's prioritisation decisions linked to resources restrictions.

The purpose of this study is to assess the long-term persistence of immunity to hepatitis A in adults who were vaccinated 21-25 years earlier with hepatitis A vaccine, Havrix®.

This is a long-term persistence study in which subjects who participated in the primary studies HAV-112 (208109/108) or HAV-123 (208109/114) and did not receive an additional dose of hepatitis A vaccine since then, will be invited to provide a blood sample at Years 21 to 25 after their second vaccine dose. No vaccine will be administered during the study period.

Inclusion Criteria:

• A male or female who received two doses of Havrix in study HAV-112 (208109/108) or HAV-123 (208109/114), and received no further booster dose since then.
• Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol (e.g. return for follow-up visits).
• Written informed consent obtained from the subject.

Exclusion Criteria:

• History of hepatitis A disease since completion of the primary vaccination series in studies HAV-112 (208109/108) or HAV-123 (208109/114).
• Administration of a hepatitis A vaccine at any time since completion of the primary vaccination series in studies HAV-112 (208109/108) or HAV-123 (208109/114) including a challenge dose of the study vaccine, as a part of the study procedures, during the long-term persistence phase.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history.
• Administration of hepatitis A immunoglobulins and/or any blood products and/or long-acting immune-modifying drugs within six months prior to study entry.
• Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to study entry. For corticosteroids, this will mean prednisone ≥ 20 mg/day, or equivalent. Inhaled and topical steroids are allowed.
• Administration of long-acting immune-modifying drugs within six months prior to study entry (e.g. infliximab).
• Concurrently participating in another clinical study during the period starting 30 days before and ending 30 days after each study visit, in which the subject has been or will be exposed to an investigational or a non-investigational vaccine/product (pharmaceutical product or device).